Equity - Monthly Distributions Declared and Paid by Company's Board of Directors (Detail) - $ / shares |
6 Months Ended | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Jun. 30, 2016 |
May 31, 2016 |
May 02, 2016 |
Mar. 31, 2016 |
Feb. 29, 2016 |
Feb. 02, 2016 |
Jun. 30, 2015 |
May 28, 2015 |
May 04, 2015 |
Mar. 31, 2015 |
Feb. 27, 2015 |
Feb. 03, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
|
| Class of Stock [Line Items] | ||||||||||||||
| Distributions per Common Share | $ 0.24375 | $ 0.225 | ||||||||||||
| Monthly Distribution One [Member] | ||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||
| Dividend Declaration Date | Jan. 12, 2016 | Jan. 13, 2015 | ||||||||||||
| Record Date | Jan. 22, 2016 | Jan. 23, 2015 | ||||||||||||
| Dividend Payment Date | Feb. 02, 2016 | Feb. 03, 2015 | ||||||||||||
| Distributions per Common Share | $ 0.040 | $ 0.035 | ||||||||||||
| Monthly Distribution Two [Member] | ||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||
| Dividend Declaration Date | Jan. 12, 2016 | Jan. 13, 2015 | ||||||||||||
| Record Date | Feb. 18, 2016 | Feb. 18, 2015 | ||||||||||||
| Dividend Payment Date | Feb. 29, 2016 | Feb. 27, 2015 | ||||||||||||
| Distributions per Common Share | $ 0.040 | $ 0.035 | ||||||||||||
| Monthly Distribution Three [Member] | ||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||
| Dividend Declaration Date | Jan. 12, 2016 | Jan. 13, 2015 | ||||||||||||
| Record Date | Mar. 21, 2016 | Mar. 20, 2015 | ||||||||||||
| Dividend Payment Date | Mar. 31, 2016 | Mar. 31, 2015 | ||||||||||||
| Distributions per Common Share | $ 0.040 | $ 0.035 | ||||||||||||
| Monthly Distribution Four [Member] | ||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||
| Dividend Declaration Date | Apr. 12, 2016 | Apr. 14, 2015 | ||||||||||||
| Record Date | Apr. 22, 2016 | Apr. 24, 2015 | ||||||||||||
| Dividend Payment Date | May 02, 2016 | May 04, 2015 | ||||||||||||
| Distributions per Common Share | $ 0.04125 | $ 0.040 | ||||||||||||
| Monthly Distributions Five [Member] | ||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||
| Dividend Declaration Date | Apr. 12, 2016 | Apr. 14, 2015 | ||||||||||||
| Record Date | May 19, 2016 | May 19, 2015 | ||||||||||||
| Dividend Payment Date | May 31, 2016 | May 28, 2015 | ||||||||||||
| Distributions per Common Share | $ 0.04125 | $ 0.040 | ||||||||||||
| Monthly Distributions Six [Member] | ||||||||||||||
| Class of Stock [Line Items] | ||||||||||||||
| Dividend Declaration Date | Apr. 12, 2016 | Apr. 14, 2015 | ||||||||||||
| Record Date | Jun. 17, 2016 | Jun. 19, 2015 | ||||||||||||
| Dividend Payment Date | Jun. 30, 2016 | Jun. 30, 2015 | ||||||||||||
| Distributions per Common Share | $ 0.04125 | $ 0.040 | ||||||||||||