Earnings per Common Share - Earnings per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic Earnings:
Net income available to common stockholders	$ 41,471	$ 87,130
Effect of dilutive securities:
Income allocated to exchangeable senior notes	1,621	5,008
Income allocated to non-controlling interest	671	1,186
Dilutive net income available to stockholders	$ 43,763	$ 93,324
Basic Earnings:
Shares available to common stockholders (in shares)	111,629	111,598
Effect of dilutive securities:
Restricted stock awards (in shares)	20	19
Non-controlling interest OP units (in shares)	1,425	1,425
Exchangeable senior notes (in shares)	4,803	15,083
Dilutive Shares (in shares)	117,877	128,125
Net income attributable to common stockholders
Basic (usd per share)	$ 0.37	$ 0.78
Diluted (usd per share)	$ 0.37	$ 0.73