Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									49,795	0	96,096
Net income	$ 9,638	$ 27,066	$ 22,638	$ 30,046	$ 21,154	$ 27,713	$ 21,911	$ 31,153	$ 89,388	$ 101,931	$ 78,236
Basic weighted average shares	196,173,169	196,062,348	195,747,954	195,745,670	195,743,154	195,743,154	195,733,692	195,720,894	195,933,800	195,735,309	195,619,943
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									2,113,653	2,117,623	939,141
Diluted weighted average shares	198,076,031	198,254,808	197,709,082	197,773,850	197,853,482	197,884,029	197,827,833	197,747,579	198,047,453	197,852,932	196,559,084
Basic net income per share	$ 0.05	$ 0.14	$ 0.12	$ 0.15	$ 0.11	$ 0.14	$ 0.11	$ 0.16	$ 0.46	$ 0.52	$ 0.40
Diluted net income per share	$ 0.05	$ 0.14	$ 0.11	$ 0.15	$ 0.11	$ 0.14	$ 0.11	$ 0.16	$ 0.45	$ 0.52	$ 0.40